The concentration of alcohol in your body is the amount of alcohol in your bloodstream.

In the ACT a driver's concentration of alcohol in their body can be measured by either or both:

in grams (of alcohol) per 100ml of blood;

in grams (of alcohol) per 210 L of breath.

For example an 0.05 concentration of alcohol in your blood means that you have 0.05 grams of alcohol in every 100ml of your blood.

Your liver metabolises alcohol at around one standard drink per hour. Your blood alcohol level will drop unless more alcohol is consumed.

A driver's concentration of alcohol is measured either by a breathalyser, or by analysing a sample of blood.

Legal concentration of alcohol limits

If you are driving the concentration of alcohol in your body must remain below a legally set level, known as the prescribed concentration.

From 1 December 2010, the prescribed concentration for those driver's classed as 'special drivers', was reduced from 0.02 grams to zero.

You are a special driver if:

the person is not the holder of an Australian driver licence, an external territory driver licence or a foreign driver licence from a recognised country; or

the person holds a foreign driver licence that:

is not issued under the law of a recognised country; or

if the licence is issued under the law of a recognised country – is a licence that corresponds to a learner licence, provisional licence, probationary licence or a restricted licence.

the person's Australian driver licence or external driver licence is suspended

the person is disqualified from holding or obtaining an Australian driver licence by a court in Australia or under the law of any jurisdiction

the person holds a learner licence, provisional licence, probationary licence or restricted licence within the meaning given by the Road Transport (Driver Licensing) Act 1999, dictionary

the person is the holder of an Australian driver licence and is driving a motor vehicle of a kind that the person is not authorised to drive by the licence

You are also a special driver if the person is the driver of:

a vehicle on which a sign, marking or placard is required to be displayed under the Dangerous Substances Act 2004 or the Dangerous Goods (Road Transport) Act 2009

a motor vehicle with a GVM of more than 15 tonne

a combination with a GCM of more than 15 tonne

a public passenger vehicle

the person is learning to drive a heavy vehicle

the person is a driving instructor who is with a driver for the purposes of driver instruction or driver assessment

the person is a heavy vehicle driver assessor who is with a driver for the purposes of driver assessment

the person is a driving supervisor who is with a person who holds a learner licence (a learner driver) while the learner driver drives a motor vehicle that displays, or ought to display, L plates on a road or road related area.

Subsection (1) (a) does not apply to a person who is exempt from holding a driver licence under the Road Transport (Driver Licensing) Act 1999.

You need to find out whether you are a special driver, as special drivers are subject to a zero concentration of alcohol in their body.

For other drivers, the prescribed concentration of alcohol in a person's blood or breath is 0.05 grams.

This means that these drivers must not drive or ride a motor vehicle if they have a concentration of alcohol in their blood or breath of 0.05 grams or more.

Factors affecting your concentration of alcohol

The more you drink, the higher your concentration of alcohol. But two people who drink the same amount might register quite different concentrations of alcohol. There are many factors that will affect this, including:

Body size:A smaller person will have a higher concentration of alcohol than a larger person because the alcohol is concentrated in a smaller body mass.

Empty stomach:Someone with an empty stomach will reach a higher concentration of alcohol sooner than someone who has just eaten a meal. Food in the stomach slows down the rate alcohol passes into the bloodstream.

Body fat:People with a lot of body fat tend to have higher concentration of alcohol because alcohol is not absorbed into fatty tissue, so alcohol is concentrated in a smaller body mass.

Women:Because of all these variable factors, counting the number of standard drinks you consume can only give a rough guide to your concentration of alcohol. For more detailed information about alcohol and how it effects you, please see the Australian Drug Foundation website.

Drinking limits advice

To keep below an alcohol concentration of 0.05 grams, drivers are advised to limit their drinking to:

For men - no more than two standard drinks in the first hour and no more than one standard drink every hour after that.

For women - no more than one standard drink in the first hour and no more than one every hour after that.

Because everyone is different, some people need to drink less to maintain a concentration of alcohol level below the legal limit.

If there is any doubt don't drive. Call a taxi, catch a bus, get a lift with someone who has not been drinking, or stay overnight.

Penalties for drink driving

The ACT's drink driving laws reinforce that drink driving is a serious offence. It can result in a jail sentence.

If the police charge you with a drink-driving offence you will be dealt with by the courts.

Penalties for drink driving offences include disqualification from driving for a set period, fines and imprisonment. You should obtain legal advice before you attend court.

Random breath testing (RBT)

Random breath testing is carried out on streets and public places at any time of the day or night.

Police officers have the right to stop any vehicle at any time and require the driver to supply a breath sample for screening.

Any person driving a motor vehicle is required by law to have less than a specified amount of alcohol in their blood.

If a driver has the specified prescribed concentration or exceeds the level which applies to them the driver has committed an offence.

RBT screening process

If the reading from a screening instrument indicates the driver of the vehicle may be the prescribed concentration of alcohol, the driver is conveyed to a police station for breath analysis.

At the police station, an authorised breath analysis operator requests the driver to supply a further breath sample for analysis by the Drager breath analysis instrument. The instrument is recognised by the ACT courts as providing an accurate and lawful reading.

If the analysis of the sample shows the person is at or over the limit, he or she can either be arrested or summoned to appear in court at a later date.

It is an offence to fail or refuse to supply a sample of breath for screening, or fail or refuse to supply a sample of breath for analysis.

Driver trainers

Driver trainers (including driving instructors, driver assessors and any person who is supervising a learner driver) can be required to undergo random breath testing.

Driver trainers are subject to a zero blood or breath alcohol concentration. That means if any alcohol is present in your blood or alcohol you commit an offence.

International drivers

Drivers who hold an international drivers licence from countries not recognised by Austroads are subject to a zero alcohol concentration.

If you are the holder of a licence—that is equivalent to a learners, provisional, probationary or restricted—issued by a recognised country you will be subject to a zero alcohol concentration.

If you are a holder of a licence issued by a recognised country, and that licence is equivalent to a full Australian licence, then you will be subject to an alcohol concentration of less than 0.05 grams of alcohol.